1. Field of the Invention
These inventions relate to doors and assemblies for display cases.
2. Related Art
Commercial refrigerators and refrigerated display cases (coolers and freezers) are used in markets, food-vending operations, liquor stores and the like for the preservation of freshness and attractive display of product to the customer. Typically, commercial display cases have extruded aluminum frames defining a rectangular opening for the case which is accessed through sliding doors or swing doors having large areas of multi-layered glazing to permit the customer to see, select and access the refrigerated product easily, while preventing heat transfer into the refrigerated space. The raw aluminum is expensive and the extrusion process also adds significant costs to the final product. After extrusion, the linear segments of rail are cut to the desired length and shape (such as to have mitered corners), punched to give holes for mounting and fastening various hardware to the frame rail, and finished to remove rough edges and the like. Four frame rail elements are used for small to medium-sized cases while more may be used for larger cases. The frame rails are fastened together at mitered corners of upper and lower horizontal frame members and left and right vertical side members, sometimes referred to as end mullions. The surrounding frame rails typically have a decorator strip, extending over the front of the case, a side-wall extending inwardly relative to the case from the decorator strip, the side-walls of the top and bottom rails supporting the hinges for the doors, and a transverse wall for mounting a contact plate against which the magnetic gasket on the door seals. The transverse wall also forms a support for center mullions in the display case. The center mullions extend vertically between upper and lower frame rails to give a sealing surface for the doors and contain wiring, ballasts or other hardware for operating lighting units mounted on the surfaces of the mullion extending into the display case. The rearwardly facing portions of the transverse walls also may support raceways or other hardware for equipment used in the unit.
The hardware for connecting the corners of the frame rail structures, and for connecting the mullions and the frame rail elements, can be complicated, with a significant number of inter-fitting parts to provide a suitable corner connection. Additionally, the processing of the frame rail elements that permits hardware such as hinges and hold opens to be mounted to the frame uses multiple steps and adds to the cost of the final product.
Typically, an extruded aluminum door rail supports and surrounds the multi-layered glazing to support the glazing panels and to protect the edges thereof. Such door rails hold the glass panels in place and extend peripherally around both the inside and outside glass surfaces of the doors. The door rails are fastened together at mitered corners of upper and lower horizontal rail members and left and right vertical side members. The hardware for connecting the corners of the rail structures also can be complicated, with their own significant number of inter-fitting parts for a suitable corner connection. Hinge elements support the door for pivoting movement relative to a vertical axis.
Extruded aluminum rail members may provide an aesthetically pleasing appearance, but are limited in terms of color and texture. While extruded aluminum elements may be formed with different profiles, a large number of frame profiles would require a significant inventory of parts.
The metal frame and door rail members, while providing suitable structural support and pleasing aesthetic appearance, readily conduct heat from outside the refrigerated display case, as well as serving as a condensation surface for water vapor which may be present in the ambient air. To reduce condensation and fogging, heater wires are sometimes placed in the frame and door rails to warm the rails and to thus inhibit condensation, especially in freezer cases. However, the consumption of energy by the heater wires adds an annual cost to the operation of the display case.
Doors are described for refrigerated display cases having one or more aspects which contribute to improved thermal efficiency, energy savings or lower manufacturing costs. In one aspect of these inventions, a display case can meet or exceed one or more thermal performance standards set by a standards association. Greater flexibility and simplicity in the manufacturing process may also result from one or more aspects of these inventions.
In accordance with one aspect of one preferred form of the inventions, a glass unit is provided for use in doors for refrigerated display cases including at least two glass panels wherein at least one surface of one of the glass panels includes a coating for reflecting electromagnetic radiation such as infrared light. The coating is preferably a low emissivity coating such as pyrolytic tin oxide having an emissivity of 0.20 or less. The coating may be applied to the inside facing surface of one or both of the glass panels, and in the case of three or more glass panels, the coating is preferably applied to the inside-facing surfaces of each of the outer-most glass panels. In accordance with a further aspect of one of the present inventions, at least two adjacent glass panels, and preferably all of the glass panels in the glass unit, are separated and spaced apart by respective spacer assemblies. At least one of the spacer assemblies is formed from a low thermal conductivity spacer, such as those commonly referred to as warm edge technology spacers. xe2x80x9cWarm edge technologyxe2x80x9d, as used herein, shall be defined as spacer material that has desiccant embedded, surrounded or incorporated in a polymeric-based seal material. Spacers incorporating warm edge technology may or may not incorporate metal structures, metal foils or other inorganic materials, but often do include such materials. For example, in one preferred embodiment, at least one of the spacers includes a metal foil extending substantially across the entire width of the spacer material between the spaced apart glass panes. The metal foil preferably acts as a barrier to the passage of gases or molecules, for example moisture.
In another aspect of one preferred embodiment of the present inventions, a glass unit is provided, for example for use as a refrigerated display case swing door, first and second glass panels have surfaces facing each other, such as inside surfaces, each having low emissivity coatings on those facing surfaces. Preferably an intermediate glass panel extends between the first and second glass panels. Each of the glass panels is separated from the adjacent glass panel by warm edge spacers. In a preferred form of one of the inventions, the glass unit includes a frame extending about and supporting at least one of the glass panels, and preferably all the glass panels, and a hinge assembly allowing the glass unit and frame assembly to swing open and closed relative to a supporting frame. Under some circumstances, a refrigerated display case door having a triple pane glass unit with the inside surfaces of the outer glass panels coated with a low emissivity coating, and with each of the glass panels separated from adjacent glass panels using spacers such as the Comfort Seal spacer can avoid using any heat on any of the glass panels that would ordinarily be used to reduce or eliminate moisture condensation. Consequently, refrigerated display cases can be designed for lower energy consumption while still maintaining clear glass for viewing product for all or a substantial portion of the time throughout a given day under normal operating conditions.
In accordance with a further aspect of one of the preferred embodiments of the present inventions, the foregoing refrigerated display case door can be constructed with spacers formed with a desiccant-embedded sealant on the inside of the spacer relative to a metal or other foil for inhibiting or blocking movement of gases across the spacer, and a sealant on the opposite side of the foil for sealing between the adjacent glass panels. A relatively harder polymeric structure is embedded in the sealant for helping to maintain the proper spacing between adjacent glass panels. Additionally, the free ends of the metal foil can each terminate at a sealing bead and sealed to the surface of the respective adjacent glass panel through the sealing bead.